In view of rising energy prices, the regulation of the idling rpm in internal combustion engines assumes ever-increasing importance because while it is desirable to have the selected idling rpm as low as possible for reasons of fuel consumption, there is a certain level of reliability that must be provided for the energy consumers in the vehicle which must be switched on and off. Air conditioners, for example, or switching gears in an automatic transmission, both of which involve an increased load on the engine such that if the safety margin beyond the lowest possible idling rpm becomes too narrow, there is a danger that the engine might stall.
A known idling rpm regulator includes a bypass conduit of controllable cross section disposed parallel to the throttle valve. The triggering is effected by means of a proportional-integral-derivative controller or PID regulator, the input variables of which are signals relating to the rpm, the actuation of the idling switch and the temperature. The bypass cross section is controlled by means of a clocked magnetic valve.
In practical operation, it has been found that with the known apparatus, the above problem cannot yet be solved optimally in terms of both fuel consumption and the lowest possible, reliably controlled idling rpm.